Natural vivianite activates peroxymonosulphate for efficient ofloxacin degradation: Performance and mechanism

Antibiotics (e.g., ofloxacin) pollution is an emerging environmental concern due to its persistence and potential health risks. Advanced oxidation processes (AOPs) offer promising solutions, yet their practical application is often limited by catalyst cost and stability. Here, we report the use of natural vivianite-a low-cost iron phosphate mineral-as an efficient peroxymonosulphate (PMS) activator for ofloxacin degradation. Under the optimised conditions, 97 % of ofloxacin was effectively degraded within 60 min. The ofloxacin degradation ratio could still reach 76 % after three consecutive cycles. Mechanistic investigations revealed Mn²⁺ and Co²⁺ isomorphic substitutions within the vivianite lattice, which induced electron cloud redistribution and promoted the formation of metal-oxygen-metal and metal-oxygen bonds. These structural changes enhanced charge transfer and facilitated PMS adsorption and activation via both surface-bound sites and leached phosphate species. Electron paramagnetic resonance spectroscopy confirmed that degradation proceeded through synergistic radical (·OH, SO₄·^-, O₂·^-) and non-radical (¹O₂) pathways. Importantly, the degradation products exhibited significantly lower toxicity than ofloxacin itself, underscoring the environmental relevance of this process. These findings highlight the potential of natural vivianite as a cost-effective and sustainable PMS activator for antibiotic removal in water treatment applications.